One thing is clear from Wednesday's announcement of a new sugary drinks tax: George Osborne knows as much about tackling obesity as Gwyneth Paltrow knows about tackling a sly Munchy Box on the way home from the pub.

It genuinely feels like our civic leaders believe they've just cracked the stubborn old chestnut that is obesity by adding 8p to a tin of ginger. Backs have been slapped, skinny people who head anti-obesity studies have fist-bumped celery sticks and Jamie Oliver has done a lap of honour around the camera crews like a puppy high on fizzing candy.

Except there are only two things this ill-conceived tax should really be seen as.

Firstly, an absurd, insulting and unfair fines system, and secondly, a massive wake-up call to our health experts and politicians, because it overwhelmingly demonstrates why our approach to tackling obesity is failing miserably.

To be clear, this is a tax aimed directly at the poor, not the overweight, because the only people it will really affect are those who go round the supermarket cagily tapping at their phone, adding up how much the shopping comes to on the calculator so they don't get a beamer at the till.

In a handy catch-all justification, George Osborne says it will raise £520m in what strikes me as a startlingly frank and early admission of its failure as a deterrent. Make no bones about it, because the Chancellor isn't, this is another mechanism by which to extract money from an already highly taxed nation, a vast chunk of whom are at financial breaking point.

I wonder if any of the following occurred to George.

How much of the money used to pay the fizzy drinks tax will come directly from benefit payments, straight out of the taxpayers' pocket and then right back into it, via increasingly browbeaten pawns?

In the Kafkaesque merry-go-round that is about to be created, how much profit will the fizzy drinks makers rake in from our shopping spend, and then re-spend on advertising their products to us in a bid to make us buy more, while a tax levied by the government to deter us from buying it is enforced upon us at the till?

What fraction of a toss will overweight Waitrose shoppers give about the increase, before carrying on to the till regardless?

Aiming to reduce the nation's intake of calorie-laden drinks is, of course, commendable, but if there is any truth in the claims a fizzy drink tax will achieve this, and that's a very big if (hotly disputed by the fizzy drinks industry, unsurprisingly), it will only do so as a distant by-product.

The other things it will do first is make poor people poorer, make thin people who like fizzy drinks poorer, add further fuel to the fat-shaming rhetoric worryingly creeping into the national conversation and reduce the amount of money some people have to spend on heating, shelter and, dare I say it, healthy food.

If it does prevent people buying fizzy drinks through poverty, then the end does not justify the means, nor does it change anything in the long run; the buyer is not shunning the sugar because of personal choice.

And why just sugary drinks? Why not all sugar-laden, overly processed, chemical-oozing products? Why not target the multinational junk food feeders which have not only infiltrated every town and city centre, service station, shopping hub, leisure park, railway station, bus station and airport in the country - but also our eyes and ears, minds and computer screens, through the relentless Ludovico Technique-style marketing that the same sugary drinks tax enforcers deem acceptable?

Obese people should not be punished, financially or otherwise. We (for, as you may have guessed, I am one) should not be shamed and prodded or treated like animals to be retrained using a fines system - especially when it is applied, quite unfairly, to those who do manage to keep their weight at medically acceptable levels.

You can't impoverish people into weight loss. It spectacularly misses the point. Nobody wants to be overweight; this is not a conscious choice or a simple case of eating too many pies.

It is complex, physiological, deep-rooted and currently eludes our most learned thinkers, so let's not waste time on ankle-high hurdles that divert crucial resources.

We need a major shift in our thinking and attitudes on obesity. We need to see it as the problem it is - an eating disorder, an insurmountable chemical compulsion to choose the wrong option, repeatedly, even when the desire to be of healthy weight far exceeds the desire to consume unhealthy food.

Can you imagine the outcry if a politician tried to claim that lowering the price of chocolate would tackle anorexia?

Scotland can lead the way in tackling this modern crisis, and earn the thanks of generations to come, but it will only do so embracing the complex issue at the root of it - which has absolutely nothing to do with the price of Irn-Bru.

Commentary by Catriona MacPhee, a digital journalist at STV. You can contact her at catriona.macphee.stv.tv.